Conformation et Spectrometrie de RMN. III. Spectres 13C de Diméthylamino Cyclanols et Dérivés

The ¹³C NMR spectra of 2-dimethylaminocyclohexanols and the four trans-3-dimethylamino-2-decahydronaphtols are described. The gauche interactions allow precise estimation of chemical shifts for each carbon atom; thus, band attribution can be resolved without mistake. In the case of the cis and the trans diequatorial compounds, the conformational perturbations which we have suggested before are verified by our present measurements on the substituted carbon atoms. We also show effects on adjacent atoms, which were unobservable with the usual IR and ¹H NMR techniques.     

Précisions apportées au mécanisme de la polymérisation du chlorure de vinyle par le chlorure de tertiobutyle-magnésium en milieu tétrahydrofurannique. Etude par résonance magnétique nucléaire

NMR analysis of the low molecular weight poly(vinyl chloride) obtained from polymerizations initiated by t-BuMgCl in THF solution suggests that all the polymer chains have the structure: Enhanced signal/noise ratio by NMR spectrum accumulation confirms this structure in products of higher molecular weights. Examination of the NMR spectrum of vinyl chloride monomer in THF solution reveals the formation of a monomer–THF complex; it seems that the initiation step of the polymerization is governed by this complexation phenomenon.     

Etude sur les composés organométalliques. XII [1]. Etude de composés tétraorganiques du titane par spectrométrie de résonance magnétique nucléaire

Tetrabenzyltitanium, tetraphenyltitanium, and tetramethyltitanium were studied by using NMR. spectroscopy. The spectrum of tetrabenzyltitanium depends on the procedure of its preparation. An interpretation of this finding is proposed.     

Etudes configurationnelles et conformationnelles de quelques chlorures de désoxy-6 β-L-héxopyrannosyle chlorosulfonyles et de leurs glycosides de méthyle

A total analysis of the NMR spectra of 6-deoxy-L -hexopyranoses in the α-configuration and of the corresponding β-anomers was carried out. The parameters obtained are characteristic of a 1C (L ) chair conformation, having the anomeric substituent in an axial orientation for the methyl α-fuco-, α-rhamno- and α-chinovopyranosides and for the α-fuco- and α-rhamnopyranosyl chlorides. The structure is also of a 1C (L ) chair type for the methyl β-fuco- and β-chinovopyranosides; the geometry is the same for the β-fuco- and β-rhamnopyranosyl chlorides despite the anomeric effect of a chlorine atom. However, the NMR parameters of the β-chinovopyranosyl chloride are not explicable on the basis of a chair conformation with an equatorial chlorine or a boat structure.     

Analyse des spectres de vibration infrarouge et Raman de benzothiazolines et de 2H-chromènes, éléments constitutifs de spiropyrannes benzothiazoliniques. Aspect synthétique

Study of infrared and Raman spectra of benzothiazolines and 2H-chromenes, constitutive parts of benzothiazolinic spiropyrans. Synthetic aspect. We have synthesized some benzothiazolines and some substituted 2 H-chromenes as models of the two halves of benzothiazolinic spiropyrans with the aim of interpretation of infrared and Raman spectra of spiropyranic structure. While doing that, we have been able to improve the synthesis method of chromenes obtained from coumarins and we have prepared new nitro-chromenes. By studying IR. and Raman spectra of the two halves of spiropyranic molecule, we could propose a rather good attribution of fondamental modes of vibration. This attribution will used as base for the interpretation of IR. and Raman spectra of a series a benzothiazolinic spiropyrans.     

Etude par spectrométrie de masse des O-isopropylidène-1,2-thréo- et -érythro-furannoses et des quatre désoxy-5-O-isopropylidène-1,2-pentofurannoses

The mass spectra of the O-isopropylidene derivatives of threo- and erythro-furanose and those of the four C(4) methylated stereoisomers have been studied. Fragmentation modes based upon deuterium labelling, metastable peaks and high-resolution measurements are proposed. Each stereoisomer can be characterized by its low-resolution mass spectrum.     

Cross‐Peaks in Simple Two‐Dimensional NMR Experiments from Chemical Exchange of Transverse Magnetisation

Two‐dimensional correlation measurements such as COSY, NOESY, HMQC, and HSQC experiments are central to small‐molecule and biomolecular NMR spectroscopy, and commonly form the basis of more complex experiments designed to study chemical exchange occurring during additional mixing periods. However, exchange occurring during chemical shift evolution periods can also influence the appearance of such spectra. While this is often exploited through one‐dimensional lineshape analysis (“dynamic NMR”), the analysis of exchange across multiple chemical shift evolution periods has received less attention. Here we report that chemical exchange‐induced cross‐peaks can arise in even the simplest two‐dimensional NMR experiments. These cross‐peaks can have highly distorted phases that contain rich information about the underlying exchange process. The quantitative analysis of such peaks, from a single 2D spectrum, can provide a highly accurate characterisation of underlying exchange processes.     

Etude par RMN protonique d'heterocycles voisins de l'oxazaphospholane-1,3,2. II—Le diméthylamino-2 méthyl-3 oxazaarsolane-1,3,2

The ¹H NMR spectrum of the 2-dimethylamino-3-methyl 1,3,2 oxazaarsolane is very sensitive to solvent and temperature. A complete analysis of the spectrum at ?48 °C in deuteriated toluene shows that the molecule exists in a preferred conformation in the C-4? C-5 region. The spectrum, corresponding to an A₂X₂ system in nitrobenzene at +31 °C, indicates free movement around that bond. At higher temperatures a new coalescence phenomenon is explained by inversion of the As atom.     

Etude de la réactivité de la fonction carbonyle avec le cétène en présence d'un alcoxyde de titane. 2e communication. A propos de l'interprétation de quelques spectres RMN de β-hydroxyesters formés

The NMR. spectra of a serie of β-hydroxyesters have been studied. It has been found that the methylene protons are magnetically nonequivalent only when the substituents on the center of asymmetry of I or II are very different. The magnetically non-equivalence of the isopropylmethylprotons arise when the β-hydroxyesters contain an aromatic or aromatic conjugated group directly bonded to the asymmetric carbon. The interpretation of this finding is proposed.     

Mise en evidence de la chiralité de l'édifice spirophosphoranique

The chirality of the spirophosphorance skeleton of the recemic mixture 2a , 2ā , is revealed by the NMR chiral shift reagent.     

Détermination de constantes de stabilité de chélates par résonance magnétique nucléaire du proton

In a solution containing an excess of two metal ions in regard to a ligand (e.g. NTA) a competitive equilibrium is established. The measure, by proton NMR. spectroscopy, of the individual concentrations of both chelates, and eventually of the free ligand, allows to determine the ratio of the stability constants of the two complexes. As an illustration the ratios of the stability constant of the 1:1 nitrilotriacetate chelates of Pb and Zn, respectively Mo and W, were determined.     

新药盐酸美利曲辛的有机波谱分析

采用核磁共振波谱(NMR)、电喷雾质谱(ESI MS)、紫外(UV)、红外(IR)吸收光谱等技术确证新药盐酸美利曲辛的分子结构;应用NOE谱技术确定盐酸美利曲辛分子中芳香氢的各自化学位移信号;解释该结构在NMR、ESI MS、UV、IR等谱图中的特征吸收峰、共振峰及特征离子的一一对应归属.     

Automated annotation and quantification of metabolites in <Superscript>1</Superscript>H NMR data of biological origin

In ¹H NMR metabolomic datasets, there are often over a thousand peaks per spectrum, many of which change position drastically between samples. Automatic alignment, annotation, and quantification of all the metabolites of interest in such datasets have not been feasible. In this work we propose a fully automated annotation and quantification procedure which requires annotation of metabolites only in a single spectrum. The reference database built from that single spectrum can be used for any number of ¹H NMR datasets with a similar matrix. The procedure is based on the generalized fuzzy Hough transform (GFHT) for alignment and on Principal-components analysis (PCA) for peak selection and quantification. We show that we can establish quantities of 21 metabolites in several ¹H NMR datasets and that the procedure is extendable to include any number of metabolites that can be identified in a single spectrum. The procedure speeds up the quantification of previously known metabolites and also returns a table containing the intensities and locations of all the peaks that were found and aligned but not assigned to a known metabolite. This enables both biopattern analysis of known metabolites and data mining for new potential biomarkers among the unknowns.     

Application de la réaction de Wittig à la synthèse de dérivés de bromoénosuloses et d'esters bromoénuroniques. Note de laboratoire

Use of the Wittig reaction for the synthesis of derivatives of bromoenosuloses and bromoenuronic esters Treatment of 3-O-benzyl (or 3-O-methyl)-1, 2-O-isopropylidene-α-D -xylo-pentodialdo-1, 4-furanoses ( 2 or 1 ) with acetylbromomethylidenetriphenylphosphorane ( 3 ), benzoylbromomethylidenetriphenylphosphorane ( 4 ) or bromoethoxycarbonylmethylidenetriphenylphosphorane ( 5 ) gave in good to excellent yields the expected enose ( 6--11 ). In all cases but one ( 8 where some 10% of the E-isomer was formed) the reaction led to the exclusive formation of the Z-isomer whose configuration was established by NMR.     

Etude par RMN du proton d'hétérocycles voisins de l'oxazaphospholane-1,3,2. I—La phényl-3 oxo-2 oxathiazolidine-1,3,2

A complete analysis of the ¹H NMR spectrum of the title compound is used for the conformational assignment of the molecule in the C-4—C-5 region. The position of protons is related to the position of the S?O bond with the help of a europium complex Eu(fod)₃. The results obtained are consistent with those found for similar compounds with or without a phosphorus atom.     

Proof of principle of a generalized fuzzy Hough transform approach to peak alignment of one-dimensional <Superscript>1</Superscript>H NMR data

In metabolic profiling, multivariate data analysis techniques are used to interpret one-dimensional (1D) ¹H NMR data. Multivariate data analysis techniques require that peaks are characterised by the same variables in every spectrum. This location constraint is essential for correct comparison of the intensities of several NMR spectra. However, variations in physicochemical factors can cause the locations of the peaks to shift. The location prerequisite may thus not be met, and so, to solve this problem, alignment methods have been developed. However, current state-of-the-art algorithms for data alignment cannot resolve the inherent problems encountered when analysing NMR data of biological origin, because they are unable to align peaks when the spatial order of the peaks changes—a commonly occurring phenomenon. In this paper a new algorithm is proposed, based on the Hough transform operating on an image representation of the NMR dataset that is capable of correctly aligning peaks when existing methods fail. The proposed algorithm was compared with current state-of-the-art algorithms operating on a selected plasma dataset to demonstrate its potential. A urine dataset was also processed using the algorithm as a further demonstration. The method is capable of successfully aligning the plasma data but further development is needed to address more challenging applications, for example urine data. Figure Traces of NMR peaks visualizing the Generalized Fuzzy Hough Transform (GFHT) method for elucidating peak correspondence between samples. The spectra are sorted according to one shift sensitive peak and reveals that other peaks exhibit a similar shift pattern. This pattern(s) can now be searched for using the GFHT. The red and black spectra in the figure are the most shifting spectra (top and bottom), by following the GFHT traces peak correspondence is easily established although peaks change spatial location Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Étude D'une Série de Phénoxazines et D'azaphénoxazines par Spectrométrie de Masse

Mass spectra of substituted phenoxazines and azaphenoxazines have been determined and are discussed here. These compounds are characterised by hydrogen on the heterocyclic nitrogen and aromatic rings with nitro groups and chlorine as substituents. The fragmentation patterns are explained by known mechanisms. An interpretation of almost all the peaks is offered. The presence of the substituents causes a complete change in the fragmentation patterns compared with the unsubstituted phenoxazine. This is due to changes in charge localisation, caused by the substituents. Isomerisation of the nitro group to the nitroso group gives rise to a particular fragmentation route.     

Etude en RMN de l'Association des Sels de Lanthanides avec des Phénols; Application à la Détermination de Structure de Polyphénols Naturels

Interaction of lanthanide salts with phenols in DMSO solution was investigated as a tool for ¹H NMR structure determination in the field of naturally-occurring polyphenolic compounds. Intermolecular competition experiments evidenced reactivity differences with respect to the nature and position of substituents. Empirical rules of reactivity are suggested from which variations observed in the PMR chemical shifts on addition of lanthanide salts to natural polyphenols (flavones, xanthones) were rationalized.     

RMN du 13C de Composés Méthylés Soufrés

A ¹³C NMR study of a series of methyl sulphur compounds is described. The results are discussed in terms of the deshielding effects on the methyl carbon exerted by –SH, –SMe, –SSMe, –SSEt, –SSMe, –SC(O)Me, –SC(S)Me, –SC(S)SMe. The ¹³C NMR chemical shifts of a series of S-methyl thioesters and dithioesters are compared with corresponding esters and connected with chemical properties.     

1H NMR and DFT study of proton exchange in heterogeneous structures of pyridine-N-oxide/HCl/DCl/H2O

Moderately narrow 1H NMR signals were observed in the solid-phase obtained from pyridine-N-oxide (PyO)...HCl solutions in acetonitrile/H2O after heterogeneous phase separation. High-resolution 1H NMR spectra are compared with those of crystalline PyO...HCl and PyO...DCl. It is concluded that partially resolved peaks in 1H NMR spectra of solids are related with heterogeneity of the spin system and the presence of different mobile H-bond clusters containing PyO, HCl, DCl and water molecules. Some part of non-bonded water or HCl molecules is captured in the cavities of crystalline samples. The attribution of the 1H NMR signals was based on the density functional theory calculation of proton magnetic screening tensor of the most expected H-bond structures in the 6-311G** basis taking into account the solvent effect by the polarized continuum model.